This is one of the devastating side affect you can get because of over masturbation. When happens is your cum extremely quick, even in fore play. I once came in my dream at the sight of seeing a naked girl. Other people can cum just by touching someone when they are aroused by them. Note that do not assume that you have Premature Ejaculation (PE) just because you encountered it once. It does mean you might have a form of PE but for PE, it has to show itself consistently. Also if you had such an experience in dream, do not count on it. Dreams are not real and having PE in dream does not mean you have PE problem! It might show you have some form of it but it does not gaurentee it.
How excessive masturbation causes PE? Well we think it is all related to the brain who we affect the brain. When you masturbate excessively you teach yourself how to cum. When you are doing is normal (you are in the mode and you want it), there is nothing wrong with it. Everything is according to the book. BUT when you are in semi aroused mode or you are just bored and you want to masturbate just to kill your time, you are teaching your organ to ejaculate no matter what. Remember your organ is lymph and it does not want any activity. When you bring it to masturbation of course by some fantasy, you are teaching it to cum even if there is less arousal. When you do this over and over, your brain finally gets in the habit to ejaculate early with less arousal. Now that it has learned it, you might want to prolong it but you can’t because you reach your goal of cumming rather quick. Also what happens is the penis mucles/tissue are affected and get somewhat weak. Again this could be a signal from the brain or may be harmone changes because of excessive masturbation. Your penis become less rigid when you are fully aroused. That means less force to shut the vein that control your ejaculation. The result you start to suffer from PE problem.
In the initial stage of PE, you will need to have an erection in order to ejaculate. If you still continue excessive masturbation, a stage comes that you will cum even without enough erection. You can ejaculate with almost a lymph penis.